Which ND filter?

[Cicero A]

Now, I am going to buy NiSi filters one at a time. I've seen people reccomend .3/.6/.9 as a starting kit.
I decided to go outside with a dslr, and set my shutter speed to 50, iso to 800(as the red is normally set to, and the f/stop to 3.5
it is bright sunlight outside as it's 3:11 pm
Now, in order for me to get an exposure right in the middle, I had to bring up my fstop from 3.5 to 16(which was 16 notches(1 stop = 3 notches i believe) AND iso from 800 to 200(6 notches).
this is a total of 22 notches on my exposure bar. every 3 moves is a stop, I believe, which means I would need just about a 7 stop nd filter to shoot in broad daylight with a good exposure(or an exposure aat 0 on the scale).
Does this sound right? Like i said, most recommend 0.3/0.6/0.9 and maybe 1.2 filters. 7 stop filter would be 2.1 so in order for me to shoot at 3.5 I would need a 2.1 filter. does this seem about right or am I missting something?

 

[Olivier Gresse]

It seems okay.

When you know that on most cameras, the max neutral filters are ND64 and that is not enough to stay open.

https://en.wikipedia.org/wiki/Neutral-density_filter

Where I live, the brightness is also very violent. So I bought a kit made of 0.3 - 0.9 - 1.5 - 2.1 and a mattebox which allows me to put two filters at the same time (even if not recommended) and to have other combinations 1.2 - 1.8 - 2.4 - 3

 

[Owen Rennie]

My most used filter is the 3 stop .9, and I find myself stacking the .9 and .6 quite a lot too. The .3 literally never gets used.

If I had to buy filters in order I'd go

.9
.6
.9 Grad ND
.6 Grad ND
1.2
Tru Pol
.3
Promist etc

 

[Cicero A]

My most used filter is the 3 stop .9, and I find myself stacking the .9 and .6 quite a lot too. The .3 literally never gets used.

If I had to buy filters in order I'd go

.9
.6
.9 Grad ND
.6 Grad ND
1.2
Tru Pol
.3
Promist etc

Are you usually shooting in mid day sunlight. If so, around what f stop are you averaging?

 

[Owen Rennie]

Yeah lots of outdoor sunny days. Lot of landscapes so 5.6-11 is popular with me

 

[Michael Lindsay]

Heavy NDs are a reality with 800asa+ cameras

With the latitude of Dragon or Alexa and Raw recording ... I am happy (ish) with a half kit.. .6, 1.2, 1.8, 2.5.... when we had 50D stock the 2.5 wasn't needed as much but now it is essential for me (aperture control)...

Now if only we could get ARcoated filters with no colour cast...

 

[Satsuki Murashige]

Now, in order for me to get an exposure right in the middle, I had to bring up my fstop from 3.5 to 16(which was 16 notches(1 stop = 3 notches i believe) AND iso from 800 to 200(6 notches).
this is a total of 22 notches on my exposure bar. every 3 moves is a stop, I believe,

The difference between f/3.5 and f/16 is 4.5 stops. Forget about 'notches' - that is just confusing you. The f/stop progression is:

f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22.

The scale extends further on each end, but this is the common range that you will find on most 35mm lenses. Each stop is half or double the amount of light, or +/- 1 stop. f/3.5 is essentially f/2.8 1/2. Since f/4 to f/16 is 4 stops, that means f/2.8 1/2 to f/16 is 4.5 stops.

Now, the ISO scale is:

25, 50, 100, 200, 400, 800, 1600, 3200 ISO.

Notice again that each value is half or double the adjacent value. Each of these steps is +/- 1 stop of light. Again, you can go higher or lower in the scale, but these are the more common whole values. Typically, ISO can be set in 1/3 stops in most digital cameras, so you will have 25-32-40-50 ISO, or 200-250-320-400 ISO. But a halving or doubling of value will always equal 1 stop. So stepping down from 800-200 ISO is a 2-stop reduction of light.

So if you combine your f/stop and ISO value changes, your total reduction of light required is 6.5 stops. Since most ND filters are commonly sold in whole stops, you would need a 6-stop ND, or ND 1.8. That is assuming you want to expose your Red camera at 800 ISO. Now of course, it is not always a bright sunny day outside so it would be smart to also buy the in-between filter densities. But if I was on a budget and could not afford every filter in the set, I would get at least: 0.3, 0.6, 0.9, 1.2, 1.8. If you simply must shoot at f/2 or f/1.4 outside in bright sunlight, then you will need even heavier NDs.